No scientific proof that diets help psoriasis
Psoriasis patients who want to see if diet can relieve their psoriasis will find programs, suggestions and anecdotes everywhere from the shelves of local bookstores to the National Psoriasis Foundation message board—everywhere but at their dermatologists' offices.
That's because stories of the success and failure of various diets are just that, says Dr. Joel Gelfand, assistant professor of dermatology and epidemiology at the University of Pennsylvania.
"Anecdotes are not proof," says Gelfand, a former member of the National Psoriasis Foundation Medical Board. "Not much is known or proven about how diet influences psoriasis, and the general feeling is the influence is not significant. Psoriasis is a very common disease, and goes into remission spontaneously 10 percent of the time, which explains the numerous anecdotes about 'cures' for psoriasis."
Gelfand says the best available data is a growing body of evidence that links psoriasis severity to obesity. Several studies have also shown a link between psoriasis and gluten intolerance in some patients. Otherwise, "there's not enough science to know at this point in time," Gelfand says.
Dr. Heather Zwickey is trying to change that.
The dean of research at the National College of Natural Medicine in Portland, Ore., Zwickey has a doctorate in immunology and microbiology from the University of Colorado-Denver. She is in the early stages of a preliminary study testing two different diets and their effect on psoriasis.
Half of the study participants will follow the "Mediterranean diet," which minimizes red meat and refined carbohydrates but includes a wide range of healthy foods, plus some foods thought to reduce inflammation such as olive oil, fish oil and red wine in moderate amounts. The other group will eat an "anti-inflammatory" diet that cuts out the foods most commonly thought to trigger sensitivities in patients.
Zwickey says she's had to rely on internal funding for the preliminary study partly because funders aren't convinced that patients will follow a strict diet long enough to produce valid results—and partly because of a conundrum faced by many people who want to study alternative treatments for diseases.
"[Potential funders] say there's not enough evidence, but you need some evidence in order to get a grant to collect the evidence," she says. She hopes the current study will set the stage for financial support from the National Institutes of Health for a larger trial.